Saturday, June 14, 2014

Know versus Feel

What you don't have you don't need it now.
What you don't know you can feel it somehow.
What you don't have you don't need it now, don't need it now.

I have already written about sensation versus intuition. This topic is slightly different, encompassing more of what is knowable in a position in which I was too lazy to calculate beyond certain feelings.

A couple friends and I got together to look at some games we played. One game ended with a won rook ending. I took the contrary position during the analysis and tried to prove a draw with best play, quoting Tarrasch's hyperbolic "All rook endings are drawn." A couple days later in a club match where I was leading 1.5-0.5, we reached the following position before Black's 20th move after an exchange of bishops on c2. I'm playing Black.

Black to move

Material is equal at 7 pawns and 2 rooks apiece. Black's pawns are more advanced on the queenside; White's a little more advanced on the kingside. White has the better center with the stonewall-like d- and f-pawns against the backward e6 pawn. I came up with a plan to attack White's d-pawn with the c5 advance, but I wanted to prepare c5 with moves such as a5-a4 and/or Kc8-c7-b6 so that white doesn't get a protected passer after c5 dxc5 {moves} b4. Much of my time on this move was spent trying to make c5 work and also trying to figure out if I needed to redeploy my rooks to the e-file in preparation for e6-e5. The problem with putting the first rook on e8 is that White could use the pin and try f4-f5. Eventually, I decided that I would double on the d-file, put my king on b6, and then advance c5 when White would probably capture dxc5 with check and then Kxc5 as long as there isn't a white pawn on b4. Once White's d-pawn is gone, then I can try to advance e6-e5. The game continued 20...Rd8. I overlooked my opponent's plans, but this didn't hurt me too much. 21.a4!?.

Black to move

Now I started to calculate what happens among the a-, b-, and c-pawns. I didn't like the fact that if I allowed axb5, I'd probably have to recapture cxb5 and then I might never remove the backwardness of the e6 pawn. If I advanced 21...b4, then 22.cxb4 axb4 23.b3 gives White a protected passed a-pawn. The third alternative was 21...bxa4 allows White's rook to enter my position with 22.Ra1 and possibilities of Rxa4xa5-a7, but I figured I have time to make trouble with 22...c5, capture on d4, maybe land a protected rook on d2 with check, and further maybe capture Rxg2. I could see that White could bail out of the rampaging rooks variation with an eventual Rxd4 in which case I would probably have to capture twice on d4 and lose the e6 pawn, but it was weak anyway, so why not give it up? So I chose this last plan. 21...bxa4 22.Ra1 c5 23.Rxa4 cxd4.

White to move

Fritz prefers 24.Rxa5 dxc3= for White versus White's choice in the game. White chose 24.Rc4+. Is is better to go Kd7 or Kb7? Kd7 looked very unattractive because it temporarily undoubles my rooks, preventing them from putting enough pressure on d4 to win a pawn. The main benefit is to protect the weak pawn at e6. If 24...Kd7 25.cxd4, I'm stuck with a backward e6 pawn again. But Fritz prefers this and concludes that 25...Rd5 favors Black by about a half a pawn. White has two isolani (b2, d4) while Black has one isolani (a5) and one backward pawn (e6). I dodged 24...Kb7 25.Rxd4 Rxd4 26.cxd4 Rxd4 27.Rxe6

Black to move

Now that my weak e6 pawn is gone, I relaxed and began to think that a draw was almost in hand. "All rook endings are drawn." I have a decision to give up my g7 pawn for his f4 pawn or defend g7 with a passive rook placement like 26...Rd7. Would I rather have the passive rook and a symmetrical pawn position or an active rook but with fractured f- and h-pawns? I chose the latter because I felt that my pawn on a5 was probably going to get surrounded if I became too passive. 27...Rxf4 28.Re7+

Black to move

A subtle point. Should Black put his pawn on b6 or c6? Fritz likes c6 by a few hundredths of a pawn. Consolidating weaknesses is one principle I try to follow. It saves a tempo if White plays Ra7, but Black would get the tempo back after Kb6 forces the rook to either back up to a8 or move off the a-file. Kc6 is slightly more central and flexible. One major disadvantage of Kb6 that I failed to appreciate is that White can indirectly defend his b2 pawn as we'll see later. 28...Kb6 29.Rxg7

Black to move

At this point in the game, I think I lost concentration. Time control was no real factor. My opponent and I each had about 40 minutes to make 1-2 moves and then we would have an hour after that. I had gotten to a rook ending with equal material. And "All rook endings are drawn." was fresh on my mind. I had threats of pinning White's king and pawns back with Rf2+. I had the slightly better king at b6 and more advanced pawns, especially a5. An aggressive line would be 28...a4 29.Kc3 (to avoid the pawn-forking Rf2+) h5 30.Rg8 h4 and White has almost no play except checking the Black king. Instead of thinking of how I could press, I felt it was time for some mindless consolidation. 29...Rf5? 30.h4 (taking advantage of Rf5?) h5 31.g3

Black to move

Thanks to my mindless play, White now has the possibility of sacrificing g3-g4 to spring the h4 pawn in a queening race. Since White's king ends up more centralized, the g-pawn is much less of a threat than the distant h-pawn. Again from the position above, I played mindlessly. 31...Kb5 32.Kc3

Black to move

In isolation, 31...Kb5 turned out to not be a dubious move, even though it gives White skewering possibilities. 31...Kc5 would have been more centralized. I forgot that the a5 pawn was still protected laterally by Rf5 as long as the rook doesn't get kicked by White's king coming to e4. An aggressive continuation I didn't even think about is 32...Rf3+ 33.Kd4 Ka4 34.Ke4 Rb3 35.Kf5 Rxb2 36.Kxf6 Rg2. But 31...Kb5 combined with the game continuation helped me lose several tempi. 32...a4?! 33.Kd4

Black to move

Because I didn't choose 31...Kc5, White's king is now aggressively centralized at d4. Because I chose 31...Kb5, a plan to attack the newly vulnerable b2 pawn with 33...Rf2 34.Ke3 Rxb2?? runs into 35.Rb7+. Because I chose 32...a4, Ka4 is not available for me to hide from a skewer. Still, 33...Rf2 is the best continuation as the Black Rook can just play tag with the White King without capturing the b2 pawn. e.g. 33...Rf2 34.Ke3 Rg2 35.Kf3 Rd2, perhaps intending Kc4 and Rxb2. Instead, I meekly avoided the skewer with 33...Kb6. Only that didn't work because White put the skewer back on the table with 34.Rg8 Rf2 35.Ke3 Rf5 36.Ke4 Rf2 37.Rh8 Ra8 38.Ra8+ Kb5 39.Rh8

Black to move

If I were looking for a draw, I should have played the repetition 39...Ka6, but I thought that Ka6 was inferior to Kc6 because if I had intended to capture Rxb2, I have to respond to Ra8+ with Kb7 dropping the a-pawn instead of allowing Rb8+ skewering to my rook at b2. But because I had done the analysis on move 33 with White's king on d4, I didn't consider that my king could now go to c4 and then b3. Ka2 appeared in some of my fantasy variations, but it's bad because of Rb4 and if the rooks come off, White's sacrifice g3-g4 wins (my move 29 comes back to haunt me). If Black tries to prevent g4 in this Ka2 line, e.g. 39...Kc4 40.Rc8+ Kb3 41.Rb8+ Ka2?? 42.Rb4 f5+ 43.Ke5 Rf3 44.Rxa4+ Kxb2 45.Rf4 Rxg3 and White still has a tablebase win. Another subtle point about rook endgames is that 39...f5+ 40.Ke3 is not so good for Black because now his pawns can be quickly gobbled by the White rook. Slowing the pawn slaughter by keeping pawns two rook moves apart is useful when time is a factor. 39...Kc6 40.Rxa5 Rxb2

White to move

Here I had fantasies of winning. I predicted 41.Ra5 Rb4+ and if 42.Kf5?? then Rb5+ starts a pawn race where I queen first. With help from Fritz, I see now that Black should come out of it with one extra pawn 43.Rxb5 Kxb5 44.h5 a3 45.h6 a2 46.h7 a1=Q 47.h8=Q Qe5+ 48.Kg6 Qxg3+ 49.Kf7 (49.Kxf6?? Qc3+ skewers) Qc7+ 50.Kg6 Qc2+ 51.Kf7 f5 with a tablebase draw. Also, it seems pretty clear that 41.Ra5 Rb4+ 42.Kf3 Kb6 43.Ra8 Kb7 44.Ra5 Kb6 is drawing. But my opponent's move here surprised me. 41.Rf5! The exclam is not so much because it's winning, but that it keeps winning chances alive for White. Notice that Rxf5+ gains a tempo because my king is not on c4. After 41.Rf5, I noticed that my a-pawn just needs some precise blocking and he could go all the way. One idea that came to me was to try to get White's king to interfere with the White rook's defense of the queening square. so I played 41...Rb4+ 42.Kf3 (it's blocking Rf1!) a3 43.Rxf6+ Kb5 44.Rf8

Diagram ABlack to move

There are about four ways to go from this diagram which I have labeled Diagram A. One easily draws. One possibly wins. One draws with difficulty. One obviously loses. My only excuse for choosing the obvious loss is that the ups and downs of draws and wins were getting to me. I still had plenty of time. I still felt that I had a draw even though White had connected passers and I was down a pawn. I even thought if White were imprecise, I could win. But the more I calculated, the more I knew that I couldn't queen the a-pawn. The disappointment of failing to queen created enough emotion that my decision making was far from objective.

If White never moves his rook, the a-pawn will never queen. Black keeps his rook on the a-file. Black can draw by either 47...Kc3 48.h5 Kb2 49.Rh1 a1=Q 50.Rxa1 Rxa1 or more easily with 47...Kd5. If the White king comes over to b2 to capture a2, Black should be able to knock out one or both of White's kingside pawns. The activity of the Black rook checking laterally from the a-file should be enough to draw easily. However, I didn't calculate deep enough to know that having White's rook trapped on a1 was enough to draw.

Now from Diagram B, with White to move, Fritz likes Black by two whole pawns, but the Shredder online tablebase says this is a draw. However, false steps from White can lead to a win for Black. Some techniques to know for Black are that having the rook on White's fourth rank is good. If a pawn tries to run offside to the sixth rank, the rook can run down a lone pawn. e.g. 48.h5 Kb3 49.h6?? Ra6 50.h7 Rh6. Having the rook on the fourth helps prevent the White king assisting in the pawns' advance. In order for White to have winning chances, he needs to get both pawns to the sixth. From Diagram B, that requires 5 tempi during which time, Black's King could have walked from h2 to f7 or f6. With Black king and Black rook watching over the queeening squares, even two pawns on the sixth would probably lose, assuming White's king is on f3. If it doesn't make sense to leave the Black rook on b4, the maneuver Rb4-Rb1-Rg1/Rh1 is also valuable. Another Tarrasch quote is "Always put the rook behind the pawn.... Except when it is incorrect to do so." The Black king would like to blockade the pawns from their front, but one of the drawing variations involved the Black king helping the rook capture a pawn from behind.

The Difficult Draw: In analyzing Diagram A, I figured I could force White's rook off the board, but I would be two tempi behind Diagram A. I didn't realize I could capture his rook on a2 because of the overlooked threat of Ra4 after Kb3. What so strange is that back in Diagram A, I recognized the threat of Ra4, but I couldn't see the same threat if I moved my king Kb5-c4-b3 or Kb5-a4-b3. I felt that my king would have to advance to b2 before I could queen the pawn at a1 and then the rook would sac for the queen: 44...a2 45.Rb8+ Kc4 46.Ra8 Kb3 47.g4?? Kb2?? 48.h5?? a1=Q?? (48...Rb3+ 49.Kf4 Ra3 still wins for Black) 49.Rxa1 Kxa1.

Diagram DWhite to move

Diagram D is a tablebase win for White beginning with 50.h6! This is what I feared when I chose the worst continuation and overlooked my chances in the first two variations.

The Obvious Loss that I chose: From Diagram A, 44...a2! 45.Rb8!+ My opponent pretended to move 45.Ra8 before releasing the rook on b8. He knew Ra8 was losing and was just messing with me. 45.Ra8?? loses to 45...Ra4 and the pawn does queen despite efforts to get back to the first rank such as 46.Rb8+ Ka5 47.Ra8+ Kb4 48.Rb8+ Ka3!. The losing move was 45...Kc5??

The Losing BlunderWhite to move

It's incomprehensible that I thought I could defend against the connected passers. I had this lame feeling that White would allow me to blockade the pawns and grab one or that I had the opportunity to distract White by queening the a-pawn and then grabbing one of his pawns. To his credit, my opponent steadily advances without giving me this chance. With threats of mate, I had to give up the a-pawn for nothing. Here's the complete game for play-through.

What I don't have now is a one-point lead in the match. It's tied at 1.5-1.5. I have White next and could still win, but I could also lose the next game and the match. This game paralleled somewhat our first encounter when he drifted through a drawish endgame and lost. In summary:

Not all rook endings are drawn.

Don't feel your way through rook endings. Know them through actual calculation.

Beware of superficial analysis. (29...Rf5?, missing that 39...Kc4 was available, missing that 47.Rxa2 is forced after 46...Kb3.)

One rook beats two pawns if they are not advanced. (Diagram B versus Diagram C)

Watch the lines where kings and rooks are treading. (Black's 31...Kb5, 33...Kb6, and 38...Kb5. White's 42.Kf3.